Mysql的底层封装

class db_mysql
{
	private $db;
	private $dbhost;//数据库主机名
	private $dbuser;//数据库用户名
	private $dbpw;//数据库密码
	private $dbname;//数据库名字
	private $pconnect;//0 =>不持久连接, 1=> 持久连接
	private $charset;//数据库编码
	var $query_num=0;//查询次数
	
	public function __construct($dbhost,$dbuser,$dbpw,$dbname,$pconnect=0,$charset="utf8")
	{
	$this->dbhost=$dbhost;
	$this->dbuser=$dbuser;
	$this->dbpw=$dbpw;
	$this->dbname=$dbname;
	$this->pconnect=$pconnect;
	$this->charset=$charset;
	$this->connect();//初始化数据库链接
	}
	//数据库链接
	private function connect()
	{
	if (!function_exists('mysql_connect')||!function_exists('mysql_pconnect')){
	$this->halt('服务器PHP不支持MySql数据库!');
	}	
	if(!empty($this->dbhost)|| !empty($this->dbuser)||$this->dbhost!=="" ||$this->dbuser!=="") {
	if($this->pconnect==1){
	$this->db=@mysql_pconnect($this->dbhost,$this->dbuser,$this->dbpw,true);
	if(!$this->db){
	$this->halt("数据库持久连接失败,可能是数据库用户名或密码错误！");
	}
	} else {
	$this->db=@mysql_connect($this->dbhost,$this->dbuser,$this->dbpw);
	if(!$this->db){
	$this->halt("数据库连接失败,可能是数据库用户名或密码错误！");
	}
	}
	} 
	if ($this->version() >'4.1'){
	mysql_query("set names ".$this->charset,$this->db);	
	}
	if(!empty($this->dbname)||$this->dbname!=""){
	if(!mysql_select_db($this->dbname,$this->db)){
	$this->halt("数据库选择失败,可能是数据库名错误！");
	}
	}
	}
	//查询执行
	function query($sql, $unbuffered = false)
	{
	$func = $unbuffered ? 'mysql_unbuffered_query' : 'mysql_query';
 	$query = @$func($sql);
	if(!$query){
	$this->halt('Query 错误
'.$sql);
	}
	$this->query_num++;
 	return $query;
	}
	//选择数据库
	function select_db($dbname) 
	{
	return mysql_select_db($dbname, $this->db);
	}
	//取单一数据(MYSQL_ASSOC,MYSQL_NUM,MYSQL_BOTH)
	function fetch($query, $result_type=MYSQL_ASSOC) 
	{
	return mysql_fetch_array($query, $result_type);
	}	
	//取结果集数据(MYSQL_ASSOC,MYSQL_NUM,MYSQL_BOTH)
	function fetch_array($query, $result_type=MYSQL_BOTH) 
	{
	return mysql_fetch_array($query, $result_type);
	}
	
	function fetch_row($query) 
	{
	return mysql_fetch_row($query);
	}
	
	function fetch_field($query) 
	{
	return mysql_fetch_field($query);
	}
	
	function fetch_assoc($query)
	{
	return mysql_fetch_assoc($squery);
	}
	//返回根据所取得的行生成的对象*
 function fetch_object($result) 
	{ 
 return mysql_fetch_object($result); 
 } 
	//返回上次UPDATE更改的行数，上次DELETE删除的行数，或上次INSERT语句插入的行数。
	function affected_rows() 
	{
	return mysql_affected_rows($this->db);
	}
	//返回结果集
	function result($query, $row = 0, $field = 0) 
	{
	return @mysql_result($query, $row, $field);
	}
	//释放结果集
	function free_result($query) 
	{
	return mysql_free_result($query);
	}

	//返回行数
	function num_rows($query) 
	{
	return mysql_num_rows($query);
	}
	//获得结果集中字段的数目
	function num_fields($query) 
	{
	return mysql_num_fields($query);
	}
	//返回插入的ID值
	function insert_id() 
	{
	return ($id = mysql_insert_id($this->db)) >= 0 ? $id : $this->result($this->query("SELECT last_insert_id()"), 0);
	}
	//错误信息
	function error() 
	{
	return (($this->db) ? mysql_error($this->db) : mysql_error());
	}
	//错误代码
	function errno() 
	{
	return intval(($this->db) ? mysql_errno($this->db) : mysql_errno());
	}
	//获取数据库版本
	function version() 
	{
	if(empty($this->version)) {
	$this->version = mysql_get_server_info($this->db);
	}
	return $this->version;
	}
	//列出 MySQL 数据库中的表
 function get_table_names($dbname='')
	{
	if(empty($dbname))
	{
	$db_name=$this->dbname;
	} else {
	$db_name=$dbname;
	}	
	$result = mysql_list_tables($db_name);
	$num_tables = @mysql_numrows($result);
	for ($i = 0; $i < $num_tables; $i++) {
	$tables[] = mysql_tablename($result, $i);
	}
	mysql_free_result($result);
	return $tables;
 	}
	function data_seek($result, $offset)
	{
	return mysql_data_seek($result, $offset);
	}	
	// 对特殊字符进行过滤value 值
	function escape_string($str){
	return mysql_real_escape_string($str,$this->db) or mysql_real_escape_string($str);
	}
	//关闭数据库
	function close() {
	return mysql_close($this->db);
	}	
	//
	function get_client_info()
	{
	return mysql_get_client_info($this->db);
	}
	//
	function get_proto_info()
	{
	return mysql_get_proto_info($this->db);
	}
	//
	function get_host_info()
	{
	return mysql_get_host_info($this->db);
	}
	//
	function field_len($result, $i)
	{
	return mysql_field_len($result, $i);
	}
	//
	function field_name($result, $i)
	{
	return mysql_field_name($result, $i);
	}
	//
	function field_flags($result, $i)
	{
	return mysql_field_flags($result, $i);
	}
	//
	function get_fields_meta($result)
	{
	$fields = array();
	$num_fields = mysql_num_fields($result);
	for ($i = 0; $i < $num_fields; $i++) {
	$field = mysql_fetch_field($result, $i);
	$field->flags = mysql_field_flags($result, $i);
	$field->orgtable = mysql_field_table($result, $i);
	$field->orgname = mysql_field_name($result, $i);
	$fields[] = $field;
	}
	return $fields;
	}
	//错误提示
	private function halt($msg='')
	{
	$s='';
	$error = $this->error();
	$errorno = $this->errno();
	
	$s.="";	
	if($this->db){
	$Version=$this->version();
	$s.="".$Version."
";
	}
	$s.="".$msg."
";
	$s.="".$error."
";
	$s.="".$errorno."
";
	die($s);
	}

}